Heating and cooling of coronal loops with turbulent suppression of parallel heat conduction 

Eduard Kontar Submitted: 20171201 06:07
Using the "enthalpybased thermal evolution of loops" (EBTEL) model, we investigate the hydrodynamics of the plasma in a flaring coronal loop in which heat conduction is limited by turbulent scattering of the electrons that transport the thermal heat flux. The EBTEL equations are solved analytically in each of the two (conductiondominated and radiationdominated) cooling phases. Comparison of the results with typical observed cooling times in solar flares shows that the turbulent mean freepath λ_{T} lies in a range corresponding to a regime in which classical (collisiondominated) conduction plays at most a limited role. We also consider the magnitude and duration of the heat input that is necessary to account for the enhanced values of temperature and density at the beginning of the cooling phase and for the observed cooling times. We find through numerical modeling that in order to produce a peak temperature ≃ 1.5 x 10^{7} K and a 200 s cooling time consistent with observations, the flare heating profile must extend over a significant period of time; in particular, its lingering role must be taken into consideration in any description of the cooling phase. Comparison with observationallyinferred values of postflare loop temperatures, densities, and cooling times thus leads to useful constraints on both the magnitude and duration of the magnetic energy release in the loop, as well as on the value of the turbulent mean freepath λ_{T}.
Authors: Bian, Nicolas; Emslie, A. Gordon; Horne, Duncan; Kontar, Eduard P.
Projects: RHESSI

Publication Status: accepted for publication in ApJ
Last Modified: 20171201 11:37


